Many components in an electronic package such as CPU, GPU, and LED light dissipate significant heat during operation, which increases the temperature of the package. This may negatively affect user experience, performance and reliability of the package. A rotary fan blowing air across high temperature regions is usually used for cooling purpose. However, the rotary fan has many disadvantages. It is generally noisy and heavy. Its efficiency and reliability are relatively low. When heavily used the fan usually fails after two to three years, and thus, cannot be used for many applications such as telecommunication and LED cooling. Moreover, it includes moving parts such as bearings and stator coils making it difficult to miniaturize.
Another type of fan is piezo (or piezoelectric) fan, which typically includes a piezo actuator attached to an elongated cantilever blade (as seen in, for example, U.S. Pat. No. 4,780,062, U.S. Pat. No. 4,923,000, U.S. Pat. No. 5,861,703, U.S. Pat. No. 7,061,161, U.S. Pat. No. 7,642,698, U.S. 2007/0090726 A1, U.S. 2011/0014069 A1, U.S. Pat. No. 8,322,889, and U.S. Pat. No. 8,581,471). The piezo fan has many advantages over the conventional rotary fan; it is simple, reliable, quiet and lightweight. When oscillating around its neutral position the blade forces the ambient air back and forth (or in and out) enhancing the rate of convective heat transfer between the air and the hot surfaces of the heated components. This fan may be useful for spot cooling in low power applications. Unfortunately, aerodynamic efficiency of the fan is very low. The fan generates very little net air flow, which greatly limits its applications.
Accordingly, the need still exists for a fan that is quiet, reliable, efficient, lightweight, and able to generate significant net air flow in a desired direction.